Fluidized Catalytic Cracking (FCC) is a well known process for converting heavy hydrocarbon feeds to lighter products. Most FCC units include a reactor and a regenerator in the fluid solids portion of the overall FCC process. The movement of catalyst between the reactor and regenerator represents a cyclical process. Heavy hydrocarbon feed is contacted with hot catalyst in the reactor to produce lighter products. During the cracking process, carbonaceous deposits or coke and other contaminants such as metals are deposited on the catalyst resulting in at least a partial deactivation of the catalyst. The deactivated catalyst is separated from the lighter products and sent to a regenerator. The coke deposits are removed from catalyst particles by burning and the regenerated catalyst recycled to the reactor. Heat from coke combustion is typically used to help maintain the desired temperature in the reactor where additional cracking of feed occurs.
Deactivated catalyst particles sent to the regenerator are first subjected to a stripping process to recover a substantial fraction of adsorbed hydrocarbon material. The recovered hydrocarbons from the stripping zone are typically added to the cracked hydrocarbons from the FCC reactor to enhance the yield of total hydrocarbon materials. These recovered hydrocarbonaceous materials are then sent for further processing to desired products. The stripped catalyst is sent to a regenerator.
In order to monitor performance of the stripping zone, it is typical to measure coke on catalyst. Current techniques for measuring coke on catalyst do not, however, differentiate between strippable hydrocarbons and non-volatile coke.
It would be desirable to maximize the yield of strippable hydrocarbon from spent FCC catalyst without using excessive stripping gas, typically steam. In order to achieve maximum yield with minimal stripping gas, it would be desirable to have a quick and reliable test for measuring strippable hydrocarbon. For example, setting the preferred stripping steam rate for a given feed composition and process conditions is typically a trial and error procedure relating regenerator conditions to steam rate changes.